The present disclosure pertains to shock absorbing feed wheel assemblies. Powered strapping machines use a feed wheel as part of a feed assembly or feed head to feed strap through a chute, retract the strap, and tension and seal the strap on the load. One known strapping machine that uses a modular feed head is illustrated and disclosed in Haberstroh, US Publication 2013/0276415, which publication is incorporated herein in its entirety. The feed head draws strap from a supply and feeds the strap around the strap chute until a lead end of the strap is received at a sealing head. The feed head then reverses to draw or retract the strap from the chute onto the load. The strap is then tensioned, cut from the supply and sealed to itself to strap the load.
The feed head has a feed motor and gearbox that drive a feed wheel to feed and retract the strap. The gearbox has a slotted output shaft. A shaft adapter is mounted to the output shaft by an output shaft key so that the output shaft and adapter rotate together. A pin is inserted through two opposing holes in the output shaft and adapter to retain the adapter feed wheel axially in place on the output shaft. One known feed head configuration is illustrated in FIG. 2.
The feed wheel is mounted to the adapter shaft in a keyed arrangement similar to the way in which the adapter is mounted to the output shaft. A spacer ring on an end of the adapter (beyond the feed wheel) and a shaft support plate with an opening to receive an end of the adapter secure the feed wheel in the assembly.
When the feed assembly reverses to draw the strap onto the load (or take-up the strap), the strap may come to an abrupt stop. This is particularly so when strapping hard or solid materials, such as metal coils, ingots and the like. As a result, the energy from the abruptly stopping strap can send a shock through the feed wheel, the adapter, the keys and the gearbox and output shaft. Such shocks can result in stresses on the keys and the adapter and can result in premature failure of the keys, adapter and gearbox.
Moreover, in this known arrangement there may be slippage between the strap being retracted and the friction surface of the feed wheel. This can result in premature wear of the feed wheel surface.
Accordingly, there is a need for a feed wheel assembly that absorbs the shock of abruptly stopping strap. Desirably such a feed wheel assembly permits feeding and retracting or taking up strap without impact on machine operations. More desirably still, such a feed wheel assembly absorbs the shock when the strap abruptly stops, and does so without allowing the strap to slip when retracted.